Motorcycle Repair: 1986 Honda CB 700sc Starter/Alternator, honda nighthawk, starter clutch

Question
Chris,
Copied below is a question asked of Mark Shively last year. My 86 cb700s has the same problem as described by "Tom". Mark's reply deals with a possible electrical issue but I'm wondering how to diagnose a possible bad starter clutch or, God forbid, a broken starter/alternator chain. My battery seems to be in good shape and spins the starter at what sounds like a fast rate. When I hit the starter button I hear a high-pitched whine. The stator on the alternator also spins. It does not engage and turn over the engine. I removed the starter and put my finger on what appears to be the clutch. It turns in both directions with just a little resistance. I bump started my bike and also noticed, after several minutes of idling, that the headlight was dimming. I'm assuming that the alternator wasn't spinning but I didn't look at that time. I have not been able to bump start it since, mostly for lack of my own endurance, or a good hill. My guess is the chain broke. My shop book relates that replacing the chain entails a complete engine tear down, top to bottom. Is that also the case to replace the clutch? My book doesn’t say. I fear the shop charge would be more than the bikes worth and I don't feel confident enough to wrench it myself. Any advice on determining the issue, clutch or chain, would be very much appreciated. I fear I may have to sell it to a salvager for parts.
Thanks,
Steve

Expert: Mark Shively
Date: 9/10/2006
Subject: 84 Honda CB700S Nighthawk Stater problems

Question
Mark,
I just bought my first bike, a 84 Honda Nighthawk 700S.  The pervious owner "just wanted to get on it and go" and had problems with the starting the bike from the starter.   He could pop start the bike andit would run just fine for a while until the bike drained the battery and then it would die.  Put a charer onthe bat, giv it a charge and the same thing all over again.  YOu can hit the starter button and you can hear the starter do its thing, but I dont' think it is turning over the engine.   I've pulled the starter and everything looks fine.  I've then went and tried to pull the alternator but can only get it to come about 1/16" out.  But I've noticed that the alternator shaft spins freely along with the gear on the back side of it that the starter would engage into. I've seen diagrams that show the Alt with a starter clutch. But I'm not sure how all this works.  Could this be as simple as a bad Battery adn its turning over the starter but not enough to engage the clutch or is the clutch messed up and I have something more serious on my hands?  It seems that the Altenator isn't supplying enough juice to the battery to keep the bike going for more than 10 min.    A point in the right direction woulkd be greatly appreciated.  

Thanks


Answer
Hi Tom,

It may be simply a defective or weak battery, but I suspect the charging system is defective.

Get a copy of the Service Manual (repair manual) and learn about testing the charging system.

Start with a fully charged battery in good condition. Using a weak or defective battery will yield inaccurate meter readings.

Perform an output test to determine the condition of the charging system. If test results are not favorable, continue testing individual components and verify their integrity.

Visit Electro Sport's website and follow their "Fault Finding Chart" for intel on testing the system.

https://www.electrosport.com/electrosport_fault_finding.html

I return tech information files by email. There was no email address with your question as requested and explained in my instructions.

Respectfully,
Mark Shively


Answer
Hi Steve.

 For analysis of problems you should always have the repair manual for the bike.  Specs will vary from each make/model as well as, sometimes, testing techniques.  It will also have the correct disassembly/assembly instructions for all aspects of the bike.

 If the stator magnet is spinning, then the engine is turning over, since it is directly connected to the crankshaft.  If any chain has failed it could be the cam chain, but the easiest way to check that is to remove the valve cover and turn the motor by hand. You should also be able to see the cam chain.

Start with that and be sure to follow the troubleshooting instructions in the manual as much as you can.

Good luck and ride safe.
FALCON